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Turnout of the voting eligible population in midterm elections since 1945, with the 2018 figure being an estimate and the highest since the 1914 midterm election which had a 50.4% turnout

On November 3, it was reported that the number of early voters was 31.5 million, which broke the 2014 record.[3] The number was raised to about 40 million ballots on November 6.[4] Some states, such as Texas and Nevada, reported that officials had received more early ballots already processed than those who voted at all in the 2014 midterm election.[4]

Michael McDonald, a professor from the University of Florida, documented the ballot numbers as they were reported and reported that the percentage turnout of eligible voters surpassed the 1966 midterm election percentage of 48.7% and that it is the largest midterm turnout since the 1914 midterm election, which had a 50.4% turnout.[5][6][7][8] Voter turnout was 50.3%, almost 13 percentage points higher than the previous midterm elections in 2014.

Twenty-three states had double-digit percentage-point increases compared to average turnout in midterm elections held between 1982 and 2014. Georgia had the greatest increase over its 1982-2014 midterm average. Its 55% turnout was 21 points higher. Texas had a turnout of 46% which was 14 points higher.[9]

The number of women who sought and won election to Congress in each election cycle from 1974 to 2018.[10][11]

A total of $5.7 billion was spent in the 2018 elections for House and Senate races, the most expensive midterm race ever.[12] The most expensive was the Florida U.S. Senate campaign, in which candidates and outside groups spent $209 million to support or oppose the candidates (Democratic nominee Bill Nelson and Republican nominee Rick Scott, the latter of whom spent over $63 million of his personal fortune on his candidacy).[12]

The 2018 elections saw a number of significant successes for women.[13] Following the 2018 election, there was a record number of women (127) in the 116th Congress, up from 110 in the previous 115th Congress. The share of women members in the 116th is 23.7 percent, up from 20.6 percent.[14][15] The number of Democratic women in the House increased by 25, while Republican women in the House declined by 10.[14] The number of women in the Senate increased by two, with both gains being Republicans (the number of Democratic women in the Senate remained the same).[16][11]

Following the 2018 election, Minnesota became the only state in which each party controlled one chamber of the state legislature. Previously, 1914 had been the most recent year in which there was only one state with a divided legislature.[19]

Following the 2018 election, Nevada became the first state in U.S. history to have an overall female majority in the state legislature, with women holding 23 of 42 seats in the state Assembly and 9 of 21 seats in the state Senate. (Women made up a majority of a state legislative chamber on one previous occasion, in the 2009-2010 New Hampshire State Senate.) Guam also elected a female majority to their territorial legislature in 2018.[20]

The 2018 elections featured a wider range and larger number of campaign advertisements than past midterm elections.[21] Nearly half of all advertisements by Democrats focused on health care, in particular on defending the Affordable Care Act (also known as Obamacare) and keeping in place protections for individuals with preexisting conditions.[22] Almost a third of Republican ads focused on taxes (in particular, the Tax Cuts and Jobs Act of 2017).[22] By mid-October 2018, over 280,000 television advertisements related to immigration, costing some $124 million, had been aired in House, Senate and governor races, "more than five times the amount spent during the 2014 midterms, when about $23 million was spent on less than 44,000 spots."[23]

In October 2018, The New York Times and The Washington Post characterized Republicans' 2018 campaign messaging as being chiefly focused on fear-mongering about immigration and race. According to The Washington Post, President Trump "settled on a strategy of fear – laced with falsehoods and racially tinged rhetoric – to help lift his party to victory in the coming midterms, part of a broader effort to energize Republican voters".[24]The New York Times wrote that "Mr. Trump and other Republicans are insistently seeking to tie Democrats to unfettered immigration and violent crime, and in some instances this summer and fall they have attacked minority candidates in nakedly racial terms".[25]Toronto Star wrote that as the mid-term elections approached, Trump resorted to "a blizzard of fear-mongering and lies, many of them about darker-skinned foreigners".[26]

In November 2018, Facebook, NBC, and Fox News withdrew a controversial political campaign ad which was backed by Trump after critics described it as racist. Shown prior to the midterm elections, the ad focused on a Migrant caravan currently traveling through Mexico with hopes of immigration to the U.S., and Luis Bracamontes, an undocumented immigrant who was convicted of killing two sheriff’s deputies in California in 2014.[27]

A number of Republican candidates claimed to support provisions of the Affordable Care Act, such as protections for preexisting conditions, even though they voted for or supported efforts that either weakened or eliminated those provisions.[28][29][30][31] Vulnerable Republican candidates who voted in favor of the American Health Care Act of 2017, which repealed portions of the Affordable Care Act, sought to defend their votes with what CNN described as "falsehoods and obfuscations".[28]

In the 2018 elections, Republicans sought to defend the Senate majority that they had maintained since the 2014 Senate elections. Thirty-five of the 100 Senate seats were up for election, including all 33 Class 1 Senate seats. Class 2 Senate seats in Minnesota and Mississippi each held special elections to fill vacancies. The Class 1 Senate elections were for terms lasting from January 2019 to January 2025 while the Class 2 special elections were for terms ending in January 2021. 24 of the seats up for election were held by Democrats, two of the seats up for election were held by independents caucusing with the Democrats and nine of the seats up for election were held by Republicans.[32] Three Republican incumbents did not seek election in 2018 while all Democratic and independent incumbents sought another term. 42 Republican senators and 23 Democratic senators were not up for election.

Assuming that the two independents won re-election and continued to caucus with them, Senate Democrats needed to win a net gain of two Senate seats to win a majority.[e] Including the two independents, Democrats held approximately 74 percent of the seats up for election, the highest proportion held by one party in a midterm election since at least 1914.[32] Prior to the 2018 elections, Nate Silver of FiveThirtyEight wrote that Democrats faced one of the most unfavorable Senate maps that any party had ever faced in any Senate election. Silver noted that ten of the seats Democrats defended were in states won by Donald Trump in the 2016 presidential election.[33][34] Meanwhile, the Class I Senate seat in Nevada was the lone Republican-held seat up for election in a state that had been won by Democratic nominee Hillary Clinton in the 2016 presidential election.[35] Silver predicted that even a nine-point victory in the nationwide popular vote for Congress would not be enough to give Democrats a majority in the Senate.[33] Some observers speculated that Republicans might be able to pick up a net of nine seats, which would give them the 60-seat super-majority necessary to break filibusters on legislation.[36]

Republicans won a net gain of two seats in the Senate. The 2018 elections were the first midterm elections since 2002 in which the party holding the presidency gained Senate seats.[32] Republicans defeated Democratic incumbents in Indiana, Missouri, North Dakota and Florida. Democrats defeated the Republican incumbent in Nevada and picked up an open seat in Arizona. All four defeated Democratic incumbents represented states won by Trump in the 2016 presidential election.[35] Democratic incumbents tallied victories in the competitive Midwestern states of Ohio, Michigan and Wisconsin as well as the key Northeasternswing state of Pennsylvania.[37]Montana and West Virginia, each of which voted for Trump by a margin of at least 20 points, also re-elected Democratic incumbents.[38] After the election, Chris Cillizza of CNN noted that by limiting their Senate losses in 2018 Democrats put themselves in position to potentially take control of the Senate in the 2020 or 2022 Senate elections.[36]

The 2018 House elections saw the largest number of retirements by incumbents of any election cycle since at least 1992.[39] By June 2018, 20 House Democrats and 44 House Republicans, including Speaker of the House Paul Ryan, had announced their retirement.[40] The disproportionate number of Republican retirements may have harmed Republican prospects in the 2018 mid-term elections due to the loss of incumbency advantage.[41][42]

Democrats had 193 seats immediately prior to the November elections, and needed to net at least 25 seats to win a majority in the House of Representatives. In the November elections, Democrats won a net gain of 40 seats. As the elections also saw Democrats fill a couple of vacant seats that had previously been controlled by the party, the Democrats won control of a total of 235 seats, while Republicans won control of at least 199 seats.[c] The net gain of 40 seats represented the Democratic Party's largest gain in the House since the 1974 elections.[43] Democrats won the nationwide popular vote for the House of Representatives by at least seven points, one of the highest margins won by either party since 1992.[41] Due in part to the surge in turnout, the total number of votes won by Democratic candidates for the House of Representatives nearly equaled the number of votes Trump won in the 2016 presidential election.[44] The 2018 elections were the third midterm elections since 2005 in which the President's party lost control of the House of Representatives.

Democrats defeated 29 Republican incumbents and picked up 14 open seats. Republicans did not defeat a single Democratic incumbent, though the party did pick up two open seats in Minnesota and one in Pennsylvania. Republicans defended the vast majority of their rural seats, but several urban and suburban seats flipped to the Democrats.[45] Many of the districts picked up by Democrats had given a majority or a plurality of their vote to Hillary Clinton in the 2016 presidential election.[46] Of the 447 individuals who served in the House during the 115th Congress, at least 104 did not win re-election in 2018—this represents the third-highest turnover rate of any election cycle since 1974.[47]

There were a total of eight special elections to the United States House of Representatives in 2018. These elections were held to fill vacancies for the remainder of the 115th Congress. As a result of the special elections held prior to November 6, Democrats won a net gain of one seat.

The vast majority of states held gubernatorial or state legislative elections in 2018. The 2018 state elections will impact the redistricting that will follow the 2020 United States Census as many states task governors and state legislators with drawing new boundaries for state legislative and Congressional districts.

Elections were held for the governorships of 36 U.S. states and three U.S. territories as well as for the Mayor of the District of Columbia. Democrats defended every seat they had controlled prior to the election and picked up seven governorships. They won open seats in Michigan, Nevada, Kansas, New Mexico and Maine and defeated Republican incumbents in Illinois and Wisconsin. They also picked up the independent-held seat in the U.S. Virgin Islands in a runoff election held November 20, 2018.[48] Most of the Democratic victories were in Democratic-leaning states or swing states. Democratic candidates ran well ahead of Hillary Clinton in South Dakota, Oklahoma, Idaho, South Carolina and other "red states" that had given large margins to Trump in the 2016 presidential. All of those candidates fell short, however, and Kansas was the lone red state to elect a Democratic governor in 2018.[49]

Republicans picked up the independent-held seat in Alaska, and Republican incumbents won election in competitive and Democratic-leaning states such as Arizona, Iowa, Massachusetts, Vermont, New Hampshire and Maryland. The party also won competitive open seat elections held in Florida, Georgia and Ohio.[50] Democrats picked up the governorship of Guam, but the incumbent Republican governor of the Northern Marianas Islands won re-election.[g]

Partisan control of congressional redistricting after the 2018 elections (note that most states will hold elections in 2019 or 2020 that could affect partisan control of the decennial redistricting that will occur prior to the 2022 elections)

Eighty-seven of the 99 state legislative chambers, in 46 states—6,069 seats out of the nation's 7,383 legislative seats (82%)—held regularly-scheduled elections.[52] Every territorial legislature except for the Legislative Assembly of Puerto Rico held elections for at least one chamber.[g] In some legislative chambers, all seats were up for election—some chambers with staggered terms held elections only for a portion of the seats in the chamber.[52][i]

Democrats gained a trifecta (control of the governor's office and both legislative chambers) in Colorado, Illinois, Connecticut, Maine, New Mexico, New York and Nevada as well as in Guam and the U.S. Virgin Islands.[58][19] Republicans lost trifectas in Kansas, Michigan, Wisconsin and New Hampshire, but gained a trifecta in Alaska.[19][59] After the election, Democrats have 14 trifectas, Republicans have 23 trifectas and 13 states have a divided government (including Nebraska, which has a non-partisan legislature).[19]

Despite these Democratic gains, the party controlled a total of just 37 state legislative chambers after the election, far fewer chambers than it had controlled prior to the 2010 elections. Tim Storey of the National Conference of State Legislatures attributed the continuing Republican dominance of state legislatures in part to Republican control of redistricting in many states following 2010.[60] In at least three states (Pennsylvania, North Carolina, and Michigan), Republicans retained control of the lower house even though a majority of voters voted for a Democratic candidate for the lower house.[61]

Following the 2018 elections, only a single state (Minnesota) had a legislature with divided control among the parties (Republicans maintained control of the state Senate while the House flipped to Democratic control). This was the first time in 104 years that only a single state had a divided legislature.[54]

A total of 157 ballot measures were voted on in 34 states. These include initiatives on redistricting reform, voting rights, marijuana, infrastructure, health care and taxes.[68]

As a result of successful ballot measures, Colorado, Michigan and Utah[69] established independent redistricting commissions while Nebraska, Utah and Idaho expanded access to Medicaid. Florida voters approved Florida Amendment 4, which restored voting rights to some felons who have served out their sentence[70] and banned off shore drilling, vaping in indoor work spaces, and gambling institutions related to dog racing.[71] Nevada and Michigan approved automatic voter registration, and Michigan expanded absentee voting. Also, Maryland approved same-day voter registration, allowing voters to register as late as on Election Day. In Arkansas and North Carolina, voter ID ballot measures were approved.[72] Michigan, Missouri and Utah voters approved marijuana proposals, with Michigan approving recreational marijuana and Missouri approving medical marijuana. Utah voters also approved medical marijuana, although Utah lawmakers later rolled back some of the provisions of the measure.[73] North Dakota voters voted down a proposal to legalize recreational marijuana.[74][75] In California, voters declined to repeal the 2017 Road Repair and Accountability Act, which increased fuel taxes and vehicle license fees to fund infrastructure improvements.[76] Nationwide, 96 transportation ballot measures worth about $30.68 billion passed at the state and local levels on Election Day—41 transportation-related ballot measures failed.[77]

Although most local offices are nonpartisan, when looking at party identification of the officeholders, registered Republicans gained two mayorships during 2018. Linda Gorton won a seat previously held by a Democrat in Lexington, Kentucky and Bob Dyer won a seat previously held by an independent in Virginia Beach, Virginia. Following the November elections, registered Democrats hold 60 mayorships (−1) in the 100 largest cities in the United States, registered Republicans hold 28 (+2) and independents hold 7 (−1).[85]

This table shows the partisan results of Congressional, gubernatorial and state legislative races held in each state and territories in 2018. Note that not all states and territories held gubernatorial, state legislative, and United States Senate elections in 2018—the territories and Washington, D.C. do not elect members of the United States Senate. Washington, D.C. and the five inhabited territories each elect one non-voting member of the United States House of Representatives. Nebraska's unicamerallegislature and the governorship and legislature of American Samoa are officially non-partisan. Several seats in the House of Representatives were vacant at the time of the election.

In Arizona, a court settlement was reached on November 9 between Democrats and Republicans after Republicans filed a lawsuit on November 7 to attempt to prevent Maricopa and Pima counties from using procedures that permit mail-in ballot fixes to occur beyond election day.[97] The settlement gave all counties until November 14 to address problems with the ballots for the state's Senate race.

Recounts of ballots were ordered for Florida's Senate, Governor and Agriculture Commissioner races on November 10 after the tallies from 67 counties were deemed too close to call.[98] Due to the recount ordered, Democratic candidate Andrew Gillum withdrew his earlier concession to Republican candidate Ron DeSantis.[99] On November 9, Republican Senate candidate Rick Scott filed two lawsuits against election officials in Broward and Palm Beach counties that alleged officials were hiding critical information about the number of votes cast and counted. While the Florida Department of Law Enforcement announced on November 9 they would not be investigating election officials,[100] a state judge ruled for the Republican candidate, that Republicans be granted "immediate" access to requested information.[101]

In total there were 8 lawsuits that were filed in the days after November 7. In Broward County, there was Rick Scott for Senate v Brenda Snipes (November 11), Rick Scott for Senate v Brenda Snipes (November 10), Matt Caldwell v Brenda Snipes (November 9), and Rick Scott for Senate v Brenda Snipes (November 8). In Palm Beach County, there was Rick Scott for Senate v Susan Bucher (November 11) and Rick Scott for Senate v Susan Bucher (November 8), along with 2 federal lawsuits; Democratic National Committee et al. v Ken Detzner (November 11) and Bill Nelson for U.S. Senate v Ken Detzner (November 8).[102] On November 19, the Supervisor of Elections for Broward County, Florida, Brenda Snipes, announced her resignation from her post, effective January 4, 2019, after national scrutiny led to widespread condemnation by Republicans.[103]

In Georgia, a judge placed a temporary restraining order on Doughterty County results on November 9 as, among other things, some of the 14,000 absentee ballots were allegedly re-routed through Tallahassee due to Hurricane Michael, resulting in a delay to the county election office certifying its results.[104][105] On November 17, Georgia Secretary of State Robyn Crittenden certified the election result, a day after the restraining order expired.[105]

Before the election there were allegations of voter suppression raised in Georgia, as well as outcry that candidate Brian Kemp did not resign from his position as Secretary of State, which oversaw the election.[106] On November 12, Democratic gubernatorial candidate Stacey Abrams filed a lawsuit to prevent two counties from rejecting absentee ballots with minor mistakes, such as if a voter moved and had not changed their address.[107]

During her concession speech on November 16, Abrams announced her plans to file a federal lawsuit challenging the way the state elections were run. She alleged that Kemp used his position of Secretary of State and its office, to aggressively purge the rolls of inactive voters, enforce an "exact match" policy for checking voters identities that left many voters in limbo and other measures to tip the election in his favor.[108]

The North Carolina Board of Elections voted unanimously on December 4 to not certify the congressional race in North Carolina's 9th district after allegations of potential wide spread election fraud in the district.[109] The board then declared a public hearing for December 21 to ensure that the election could be declared without fraud or corruption.[110]The Washington Post reported on December 5 that the board had collected as evidence of election fraud six sworn statements from voters in Bladen County alleging that individuals called on them to pick up their absentee ballots.[109]

Incoming Democratic Majority Leader Steny Hoyer announced that the House of Representatives would not seat the apparent winner, Republican Mark Harris, until the fraud investigation had been completed, leaving it vacant at the start of the 116th United States Congress.[111]

After a delay caused by a restructuring of the board, hearings resumed on February 18, 2019. On that day the regulator reported that it had found evidence of "a coordinated, unlawful and substantially resourced absentee ballot scheme" that may have involved more than 1,000 ballots or ballot request forms.[112] The board then unanimously voted on February 21, 2019, to call a new election.[113]

In May 2018, President Trump began to emphasize his effort to overcome the traditional strength of the non-presidential party in midterm elections, with "top priority for the White House [being to hold] the Republican majority in the Senate". He was already at that time well into his own 2020 reelection campaign, having launched it on inauguration day, 2017. In May, on a trip to Texas for a Houston fundraiser targeting the midterms, he also held a fundraising dinner in Dallas for the 2020 campaign.[114] By early August, the President's midterm efforts had included rallies in Ohio, Pennsylvania, Florida, Montana and elsewhere "reprising the style and rhetoric of his 2016 campaign". Democrats "need to flip 23 seats to capture the speaker's gavel", USA Today put it. The President was addressing the economy, the border wall, the "trade war", "don't believe anything" and the space force in the rallies, per the report.[115]

In late August 2018, controversy surfaced about the degree of campaigning being done on what were termed "official" visits around the country. One report said, traditionally, partisan attacks and endorsements were kept out of official events but that President Trump was not observing that norm. Beyond the norm, one commentator was quoted referring to "laws designed to prevent taxpayer resources from being used for self-serving purposes – in this case, for campaign purposes". White House-recognized individuals "familiar with the president's thinking" spoke without attribution on a conference call and in another call about the campaigning. The individuals identified 35 events by Cabinet and senior staff members "with or affecting House districts in August already [...] [all] targeted districts" and described a July 26 presidential trip, presented as "official", as having been "for" Rep. Rod Blum of Iowa and Rep. Mike Bost of Illinois. The White House (via deputy press secretary Lindsay Walters) responded to the report: "It is unfortunate but ultimately unsurprising that a liberal publication like Huffington Post would make these misleading accusations and misconstrue the intent of the response".[116]

Director of National Intelligence Dan Coats stated during congressional testimony that "the United States [was] under attack" from Russian efforts to impact the results of the elections.[117] As of February 13, 2018, six U.S. intelligence agencies unanimously reported their conclusion[118] that Russian personnel were monitoring American electoral systems and promoting partisan causes on social media.[119] On May 23, 2018, United States Secretary of StateMike Pompeo warned in a committee hearing that the Federal government of the United States was not adequately protected from Russian interference in the 2018 midterm elections, saying: "No responsible government official would ever state that they have done enough to forestall any attack on the United States of America".[120]

On July 16, 2018 at a summit in Helsinki with Vladimir Putin, U.S. President Donald Trump downplayed the conclusions of the United States Intelligence Community, stating that he believed Putin's repeated denials of interference in American elections. Later, President Trump answered "no" in response to questions asking if he believed Russia would be targeting the midterm elections; he later claimed he was refusing to answer the question, not responding to it. In late July, the President said in a tweet that he was "very concerned" about allegations of Russian meddling, but added that he believed interference would only benefit Democrats.[121]

On July 26, 2018, Democratic U.S. Senator Claire McCaskill from Missouri alleged that Russian hackers unsuccessfully attempted to break into her Senate email account,[122] confirming a report in The Daily Beast.[123]

On August 2, 2018, Coats—along with FBI Director Christopher Wray—announced at a White House press conference that Russia was actively interfering in the 2018 elections.[124] Also on August 2, 2018, NPR reported that Democratic U.S. Senator Jeanne Shaheen from New Hampshire reported to the FBI several attempts to compromise her campaign[125] including both spearphishing attempts on her staff and a disturbing incident where someone called her offices "impersonating a Latvian official, trying to set up a meeting to talk [about] Russian sanctions and about Ukraine". Her opposition to Russian aggression and support of sanctions had placed her on an official Russian blacklist.[126]

On August 8, 2018, U.S. Senator Bill Nelson from Florida told the Tampa Bay Times that Russian operatives had penetrated some of Florida's election systems ahead of the 2018 midterm elections. "They have already penetrated certain counties in the state and they now have free rein to move about", Nelson told the newspaper. He also stated that more detailed information was classified.[127] The Russian hackers may be able to prevent some voters from casting votes by removing people from the voter rolls.[128] Nelson provided no evidence of Russian hacking and was criticized by The Washington Post's Fact Checker, who gave Nelson's claim four Pinocchios as an outright lie.[129]

In a September 2018 speech at the United Nations Security Council and Twitter posts, Trump made no mention of Russian interference, but accused China of meddling in the U.S. midterm elections, asserting that "they don't want me or us to win" because of his imposition of tariffs on Chinese goods.[130] China's Foreign Minister, Wang Yi responded by stating that "we did not and will not interfere in any countries' domestic affairs. We refuse to accept any unwarranted accusations against China".[131] While the Chinese government has used its cyber-warfare capacities for espionage and to monitor Chinese dissidents overseas, there is no evidence that China used its cybercapabilities to interfere in the 2018 U.S. elections.[130]

On December 22, 2018, Coats reported that there was no evidence of vote tampering, but that "influence operations" had persisted. "The activity we did see was consistent with what we shared in the weeks leading up to the election. Russia, and other foreign countries, including China and Iran, conducted influence activities and messaging campaigns targeted at the United States to promote their strategic interests".[132]

Republican President Donald Trump and Democratic House Minority Leader Nancy Pelosi each declared victory for their respective parties in the 2018 elections

Democratic control of the House of Representatives means that they can prevent the passage of Republican legislation in the 116th United States Congress which will meet from January 2019 to January 2021. The party will also gain control of congressional committees with the power to issue subpoenas and investigate various issues. However, by keeping control of the Senate Republicans will be able to confirm President Trump's nominees without Democratic support.[133]

After the election, despite the Democratic takeover of the House, President Trump stated that he had won a "big victory". He indicated that he looked forward to "a beautiful bipartisan-type situation," but promised to assume a "warlike posture" if House Democrats launched investigations into his administration. House Minority Leader Nancy Pelosi stated that her party won gains because of voter desire to "[restore] the Constitution’s checks and balances to the Trump administration".[134] Senate Minority Leader Chuck Schumer stated that Senate Democrats performed "much better than expected" in a difficult election cycle.[135] Senate Majority Leader Mitch McConnell stated that election day was "a very good day" for his party.[136]

The election was widely characterized as a "blue wave" election.[137][138][139][140] At the end of election night, Democratic gains in the House appeared modest and the Democratic candidates trailed in Senate races in Arizona and Montana and looked set to make a net loss of as many as four Senate seats, leading some news outlets to characterize the election as a "split decision" whereas other outlets described it as a "blue wave".[141][142] However, over the next days and weeks, Democrats won several seats in the House and won the Arizona and Montana Senate elections, leading to a re-evaluation of the initial election night analyses.[143][144] One week after the election, Nathaniel Rakich of FiveThirtyEight stated that the election was "by any historical standard, a blue wave".[137] Two weeks after the election, Nate Silver of FiveThirtyEight wrote: "There shouldn’t be much question about whether 2018 was a wave election. Of course it was a wave".[139] It was third-largest midterm change of seats for either party in the House in the post-Watergate era,[138] and the largest Democratic House gain since 1974.[145]Gerrymandering and voting restrictions prevented larger gains for the Democratic Party.[146][147][148][149] In two of the most heavily gerrymandered states, Ohio and North Carolina, Democrats failed to pick up a single seat despite winning close to half the vote. Despite almost winning half the vote in Ohio, Democrats only controlled a quarter of its House seats.[146] Democrats also made among the largest gains in House seats in Pennsylvania, where the state Supreme Court had struck down a heavily gerrymandered map that favored Republicans.[149]

^ abDemocrats won a net gain of 40 seats on election day, but gained one more seat in a special election held earlier in 2018. One House race in North Carolina has not been certified due to allegations of election fraud.

^Democrats needed to win 51 seats to acquire a Senate majority. In a hypothetical tied Senate where each caucus had 50 senators, the vote of Republican Vice President Mike Pence would have given Senate Republicans the majority.

^ abThe 2018 general election in the Northern Marianas Islands were delayed until November 13 due to Typhoon Yutu, which struck the territory shortly before the scheduled November 6 election date.

^States labeled as "no redistricting necessary" currently only have one congressional district, and thus do not need to redistrict. However, some projections show that, prior to the next round of redistricting, Rhode Island could lose its second district and Montana could gain a second district.[51]

^ abOne of Vermont's senators, Patrick Leahy, is a Democrat. The other senator from Vermont, Bernie Sanders, was elected as an independent and has caucused with the Democrats since taking office in 2007.

^ abThe Democratic Senate caucus consisted of 47 Democrats and 2 independents prior to the 2018 elections and 45 Democrats and two independents after the elections.

^ abWashington, D.C. does not elect a governor or state legislature, but it does elect a mayor and a city council.

^ abAlthough elections for governor of American Samoa are non-partisan, Governor Lolo Matalasi Moliga has affiliated with the Democratic Party at the national level since re-election in 2016.

^ abDelegate Gregorio Sablan was elected as an independent, but he has caucused with the Democrats since taking office in 2009.

^ abPuerto Rican Governor Ricardo Rosselló was elected as a member of the New Progressive Party and affiliates with the Democratic Party at the national level.

^ abPuerto Rico's Resident Commissioner, Jenniffer González, was elected as a member of the New Progressive Party and has caucused with the Republicans since taking office in 2017.